The novelty effect of an enrichment device is important relative to animal husbandry and the optimal schedule for changes of enrichment devices. Previous studies investigating the topic of environmental complexity have dealt mainly with the neophobic response of rodents to novel foods or liquids. The literature concerning primate neotic responses reveals that monkeys reared in isolation exhibit more fear of unfamiliar objects than do feral and mother-peer reared and that when exposed to a series of novel objects, chimpanzees become less fearful of new objects. The objective of this study is to address the influence of environmental complexity on the primate's reactions to novel objects. Two separate housing facilities were used for the study: one with a typical enrichment program and one with a more complex and diverse program. Eight rhesus monkeys (Macaca mulatta) housed in pairs were used for the study. An A- B-A paradigm was used. Behavioral data was collected. Each animal was observed 15 minutes a day, 3 days a week for two weeks prior to receiving a novel object in or on the cage. They were then observed for the same amount of time with a novel object (mirror, wishbone shaped dog toy, split PVC pipe, knotted dog bone). The object was changed every two weeks, for a total of 8 weeks. Finally, they were observed for 2 weeks following the removal of the last novel object. The data have been collected and are being analysed.